The Research Of Adaptive Equalization Technology For Wireless Communications

In the wireless communications, the inter-symbol interference (ISI) because of multi—path transmission influence, the received signal bring error codes, but communication protocols require send over date-frames of bring error codes, thereby influence the speed of transmitted signals in the wireless communications channel. The adaptive equalizer technique can compensate the distortion caused by the change of the channel parameter and counteract the attenuation of the channel signal, at the same time it can eliminate the ISI efficiently and then decrease coding errors and enhance the transmitting rate as well, thus the adaptive equalizer technique is utilized extensively in the communication system.On the basis of studying on wireless communication channels, this paper discusses the appearance of ISI, introduces Nyquist first rule and the theory of time-domain equalizer. The equalizer structures and the adaptive algorithm are particularly studied in this paper. Introduce linear transversal equalizer (LTE), decision feedback equalizer (DFE) and maximum likelihood sequence estimation (MLSE) in the equalizer structures; present a hybrid-type DFE. Study the behavior of three kinds of the algorithm---LMS algorithm, RLS algorithm and CMA algorithm in this paper, present two modified CMA algorithm--- varying step-size CMA and modified CMA, faster than common CMA algorithm in convergence speed. Simulate comparing LMS algorithm and RLS algorithm in the LTE and DFE, the best behavior of eliminate ISI is RLS algorithm DFE. Finally, we present the realization of the DSP based adaptive equalizer hardware systems, software systems and algorithm in detail.